The present invention relates to an automatic chemical analyzer for continuously obtaining photometric data on a plurality of reaction tubes into which samples and reagents are dispensed, while moving the reaction tubes along an endless arrangement line.
FIG. 1A shows an example of a conventional automatic chemical analyzer for chemically analyzing human serum and the like.
In this analyzer, a plurality of reaction tubes 101a to 101l are arranged on ring-shaped holder 102, which is arranged on a rotating table (not shown). For simplicity, the analyzer of FIG. 1A is shown as using only 12 reaction tubes 1a to 101l, although an actual analyzer would use several times this number. Tubes 101a to 101l are made of glass or other material which transmits light. As the rotating table rotates, the reaction tubes are rotated in regular cycles, in the direction indicated by arrow Y in FIG. 1A.
Ring-shaped holder 2 is surrounded by a washing unit, a sample dispensing unit, a first-reagent dispensing unit, a first stirring unit, a second-reagent dispensing unit, and a second stirring unit, none of these units being shown in FIG. 1A. Washing positions A for the washing unit, sample dispensing position B for the sample dispensing unit, first-reagent dispensing position C for the first-reagent dispensing unit, first stirring position D for the first stirring unit, second-reagent dispensing position E for the second-reagent dispensing unit, and second stirring position F for the second stirring unit are set individually at predetermined stop positions for reaction tubes 101a to 101l. In these individual positions, specified operations of the analyzer are performed viz-a-viz the reaction tubes.
In the stop state shown in FIG. 1A, reaction tubes 101b, 101c, and 101d are washed at washing positions A. Samples (e.g., serum) and reagents, dispensed into and mixed in the reaction tubes before reaching positions A, are washed away. In sample dispensing position B, a sample is dispensed to reaction tube 101a, which has been washed in the previous cycle. In first-reagent dispensing position C, a first reagent is dispensed into reaction tube 101l, into which a sample was injected when, in the previous cycle, it was at sample dispensing position B. In first stirring position D, a sample in reaction tube 101k, is stirred together with the first reagent which was injected thereto when, in the previous cycle, reaction tube 1k was at first-reagent dispensing position C. In second-reagent dispensing position E, the second reagent is dispensed into reaction tube 101i, in which, in the last cycle but one, a sample and the first reagent were stirred. In second stirring position F, a sample and the first and second reagents in reaction tube 101h, the second reagent having been injected thereinto in the previous cycle, are stirred. Numeral 103 denotes a photometric system, which includes light source 104 and light sensing element 105. Light emitted from light source 104 crosses the path of transfer of reaction tubes 101a to 101l, and is received by sensing element 105. When moving tubes 101a to 101e intercept the light emitted from source 104 toward element 105, the quantity or intensity of light transmitted through tubes 1a to 1l vary, depending on the contents of the tubes. Thus, sensing element 105 detects, as photometric data, absorbances corresponding to the quantity or intensity of light transmitted through tubes 1a to 1l.
After the stationary state of reaction tubes 1a-1l shown in FIG. 1A has continued for a predetermined period of time, ring-shaped holder 102 is rotated in the direction of arrow Y for another predetermined period of time. After moving reaction tubes 1a to 1l in this manner, holder 102 is stopped again
If the interval between each two adjacent reaction tubes is designated as a pitch, ring-shaped holder 102 is rotated for one revolution plus one pitch, starting from the stationary state shown in FIG. 1A. FIG. 1B shows the arrangement of reaction tubes 1a to 1l following such rotation of holder 102. In the stationary state shown in FIG. 1B, specified operations are performed for tubes 1a to 1l in their respective positions, just as in the stationary state shown in FIG. 1A.
A cycle is defined as a combination of the stop time and the time during which reaction tubes 1a to 1l move. As such a cycle is repeated, tubes 101a to 101l advance pitch by pitch. Thus, photometry can be successively performed with respect to the reaction tubes.
Photometric data is based on a photometric value obtained at time t.sub.b, which is .DELTA.t after time t.sub.a, as shown in FIG. 2B. (At time t.sub.a, optical axis X of the light from light source 104 is intercepted by any of reaction tubes 1a to 1l, as shown in FIG. 2A). Time t.sub.b is the instant when the light from light source 4 passes through the axis of each moving reaction tube.
FIG. 3 shows photometric data obtained as a result of rotation of holder 102 from the stationary state of FIG. 1A to the stationary state of FIG. 1B, i.e., for one cycle (one revolution plus one pitch). When holder 102 starts to rotate in the direction of arrow Y, from the position of FIG. 1A, reaction tubes 101f and 101g are measured photometrically at times t.sub.1 and t.sub.2, respectively. After such photometric operation is repeated in succession, tube 101f is measured again at final time t.sub.13. Thus, absorbances Q.sub.1 to Q.sub.13 of the contents of reaction tubes 1a to 1l can be obtained.
In executing the photometric operation described above, the time for each cycle is equal to the sum of the time during which the reaction tubes are rotated and the time during which holder 2 is stationary. Thus, if the rotating time and stop time are each 10 seconds, the cycle time is 20 seconds.
If, for example, the photometric processing capacity is to be increased, then the cycle time must be reduced. However, reduction of the stop time of holder 102 is restricted by various factors. Therefore, it may only be possibe to shorten the cycle time by reducing the rotating time, say from 10 seconds to 5.
If the rotating speed of holder 102 and the moving speed of reaction tubes 101a to 101l are increased at the same time, however, photometric system 103 will then be adversely affected by the resultant vibration. As a result, it becomes difficult to perform photometry at an appropriate point. Therefore, measurement errors tend to occur.
With the aim of solving these problems, the present inventor is his unpublished research defined one cycle of rotation of holder 102 is defined as a half revolution plus one pitch, instead of one revolution plus one pitch, and without a change in the rotating speed (e.g., one rotation for 10 seconds) of the holder. If one cycle of rotation of holder 102 is defined as above, the cycle time can be reduced, for example from 20 seconds to 15 seconds. FIG. 4 shows the arrangement of reaction tubes 101a to 101l after the holder is rotated for a half revolution plus one pitch, starting from the stationary state shown in FIG. 1A.
In this example, the number of reaction tubes 101a to 101l is an even number (12). When holder 102 is rotated for a half revolution plus one pitch, in this case, total number P of pitches covered in each cycle is given by P=(n/2)+1, where n is the total number of reaction tubes 101a to 101l. Thus, the state shown in FIG. 4 is that which is in being after reaction tubes 1a to 1l are moved for 7 pitches (P=(12/2)+1=7), in the direction of arrow Y, starting from the stationary state shown in FIG. 1A. When the next cycle of rotation is executed, reaction tubes 101a to 101l are moved for another 7 pitches, in the same manner, and then stop.
Reaction tube 101a is observed attentively with every cycle of rotation, to follow up and determine the rotational positions to which reaction tubes 1a to 1l are moved. FIG. 5 shows the result of such observation. In FIG. 5, (1) corresponds to the stop position of reaction tube la as shown in FIG. 1A, and (2) indicates a stop position reached after one cycle of rotation for a 7-pitch movement. Likewise, (13) to (12) indicate stop positions reached after the following individual cycles of rotation. This result applies also to all of the 11 other reaction tubes, with the exception of the first stop position. The larger the figures indicative of the stop positions for reaction tubes 1a to 1l, the more advanced is the reaction in the reaction tubes. After the reaction is advanced to some degree, tubes 101a to 101l are washed. If the progress of the reaction is on a certain level, the last stop position (position (12) in this example) need not always be reached before the washing takes place. Thus, the time for performing washing can be determined freely, depending on the particulars of measurement.
If the arrangement of reaction tubes 101a to 101l shown in FIG. 5 is observed from such a point of view, it can be seen that the reaction tubes at positions (8) to (12), which are to be washed, for example, are situated randomly on ring-shaped holder 102. This means that washing positions A cannot then be situated collectively in specific continuous regions around holder 102. Structurally, therefore, the analyzer requires the provision of idle spaces, with the result that it cannot be as compact as desired.
Thus, in the automatic chemical analyzer of the inventor's unpublished research, reaction tubes 101a to 101l are rotated for a half revolution plus one pitch in each cycle, in order to shorten the cycle time. In this case, washing positions A cannot be situated collectively in continuous regions if the number of reaction tubes 101a to 101l is an even number. Consequently, such an analyzer cannot easily be made compact.